Methods and apparatus for testing earth formations

ABSTRACT

In the representative embodiments of the new and improved methods and apparatus for testing earth formations disclosed herein, fluid-admitting means are placed into sealing engagement with a potentially-producible earth formation and selectivelyoperable valve means are rapidly opened to place a low-pressure chamber and a flow line in the tool into communication with the isolated formation to remove plugging materials from a filtering medium ahead of the flow line before connate fluids are inducted into the tool as well as to obtain one or more preliminary pressure measurements which are indicative of the potential success of the testing operation and the possible nature of the earth formation.

United States Patent 1191 Urbanosky [4s] May21, 1974 METHODS AND APPARATUS FOR TESTING EARTH FORMATIONS [75] Inventor: Harold J. Urbanosky, Pearland,

Tex.

[73] Assignee: Schlumberger Technology Corporation, New York, NY.

[22] Filed: Dec. 8, 1972 [21] Appl. No.: 313,236

[52] US. Cl. 73/155 [51] Int. Cl. E211) 49/00 [58] Field of Search 73/155, 421 R, 151, 152;

[56] References Cited UNITED STATES PATENTS 3,011,554 12/1961 Desbrandes et al. 166/100 3,254,531 6/1966 Briggs, Jr. 73/155 3,352,361 11/1967 Urbanosky 166/100 3,530,933 9/1970 Whitten 166/100 3565169 2/1971 Bell 166/100 5/1971 Lebourg 73/152 4/1972 Anderson et al. 166/100 Primary Examiner-Jerry W. Myracle Attorney, Agent, or Firm-Ernest R. Archambeau, Jr.;

William R. Sherman; Stewart F. Moore ABSTRACT In the representative embodiments of the newand improved methods and apparatus for testing earth formations disclosed herein, fluid-admitting means are placed into sealing engagement with a potentiallyproducible earth formation and selectively-operable valve means are rapidly opened to place a lowpressure chamber and a flow line in the tool into communication with the isolated formation to remove plugging materials from a filtering medium ahead of the flow line before connate fluids are inducted into the tool as well as to obtain one or more preliminary pressure measurements which are indicative of the potential success of the testing operation and the possible nature of the earth formation.

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METHODS AND APPARATUS FOR TESTING EARTH FORMATIONS Heretofore, the typical wireline formation testers (such as the tool disclosed in U.S. Pat. No. 3,01 1,554) which have been most successful in commercial service have been limited to attempting only a single test ofone selected formation interval. Those skilled in the art will appreciate that once one of these typical tools is positioned in a well bore and a sampling or testing operation is initiated, the tool cannot be again operated without first removing it from the well bore and reconditioning various tool components for another run. Thus, even should it be quickly realized that a particular sampling or testing operation already underway will probably be unsuccessful, the operator has no choice except to discontinuethe operation and then return the tool to the surface. This obviously results inaneedless loss of time and expense which would usually be avoided if another attempt could bemade without having to remove the tool from the well bore.

One of the most significant problems which have heretofore prevented the production of a commercially successful repetitively-operable formation-testing tool has been in providing a suitable arrangement forreliably establishing fluid or pressure communication with incompetentfor unconsolidated earth formations. Although the several new and improved testing tools respectively shown in U.S. Pat. Nos. 3,352,36l, 3,530,933. 3,565,169 and 3,653,436 are especially arranged for testing unconsolidated formations, for one reason or another these tools are not adapted for performing more than one testing operation during a single run in a given well bore. For example, as described in these patents, each of these new and improved testing tool employs a tubular sampling member which is cooperatively associated with a filtering medium for preventing the unwanted entrance of unconsolidated formation materials into the testing tool. Experience hasshown, however, that although these new and improved filtering arrangements are highly successful for a single operation, subsequent tests cannot be reliably performed since particles of mudcake and exceptionallyfine formation materials will often coat or plug the filtering medium. Thus, following each test, the testing tool must be returned to the surface and the filtering medium thoroughly cleaned of these plugging materials to achieve an acceptable level of operating reliability..

In addition to being unsuited for repetitive testing, tehse testing tools are incapable of providing preliminary measurements which would be indicative of the nature of an earth formation before testing or sampling is commenced.

Accordingly, it is an object of the present invention to provide new and improved formation-testing methods and apparatus for reliably obtaining one or more preliminary pressure measurements whichwill be indicative of the potential success of a subsequent testing or sampling operation of the characteristics of an earth formation.

This and other objects of the present invention are attained in the practice of the new and improved meth ods described herein by placing normally-closed fluidadmitting means having filtering means cooperatively arranged therein into sealing engagement with an earth formation, quickly opening communication between the earth formation and an enclosed low-pressure ratus l6 and a power supply chamber at a speed sufficient to induce a sudden flow or surge of connate fluids through the filtering medium and-into the test chamber for cleansing the filtering medium of unwanted possibly plugging matter as well as obtaining one or more presure measurements which are indicative of the potential success of a sampling operation and the possible nature of the earth-formation. To achieve the objects of the present invention, formation-testing apparatus is provided with fluidadmitting means adapted to be sealingly engaged with a potentially-producible earth formation. To limit the entrance of loose formation materials into the fluidadmitting means, filtering means are disposed in communication with the fluid-admitting means. Normallyclosed valve means are cooperatively arranged in the fluid-admitting means for selective rapid movement to an open position for quickly opening communication between an isolated earth formation and an enclosed low-pressure chamber downstream of the filtering means to move or divert possibly-plugging materials away from the flow path of fluids passing through the filtering means. Means are further provided for obtaining one or more pressure measurements in the chamber upon opening of the valve means to make a preliminary determination of the chances for a successful test.

The novel features of the present-invention are set forth with particularity in the appended claims. Theinvention, together with further objects and advantages thereof, may be best understood by way of the following description of exemplary apparatus employing the principles of the invention as illustrated in the accompanying drawings, in which:

FIG. 1 depicts the surface and downhole portions of a preferredembodiment of new and improved formation-testing apparatus for practicing the invention and incorporating its principles;

FIGS. 2A and 28 together show a somewhatschematic representation of the formation-testing tool illustrated in FIG. 1 as the tool will appear in its initial operating position;

FIGS. 3, 4, 5A and 58 respectively depict the successive positions of various components of the new and improved tool shown in FIGS. 2A and 28 during the course of a typical testing and sampling operation; and

FIGS. 6A-6Dschematically illustrate various typical pressure measurements which would beobtained under difierent situations while performing the new and improved methods of the present invention with the tool shown in FIGS. 2A and 28.

Turning now to FIG. 1, a preferred embodiment of a new and improved sampling and measuring tool 10 incorporating the principles of the present invention is shown as it will appear during the course of a typical measuring and sampling operation in a well bore such as a borehole ll penetrating one'or more earth formations as at 12 and 13. As illustrated, the tool 10 is suspended in the borehole 11 from the lower end of atypical multiconductor cable 14 fashion on a suitable winch (not shown) at the surface and coupled to the surface portion of a tool-control system 15 as well as typical recording and indicating appa- 17. In its preferred embodiment, the tool 10 includes an elongated body 18 which encloses the downhole portion of the tool control system 15 and carries selectively-extendible toolanchoring means 19 and new and improved fluidthat is spooled in the usual.

3 admitting means 20 arranged on opposite sides of the body as well as one or more tandemly-coupled fluidcolle'cting chambers 21 and 22. i

As is explained in greater detail ina copending application, Ser No. 313,235 by Harold J. Urbanosky filed on Dec. 8, 1972, the new and improved formationtesting tool "and the control system are cooperatively arranged so that, upon command from the surface, the tool can be selectively placed in any one or more of five selected operating positions including those required to practice the new and improved methods of the present invention with the testing tool. As will be subsequently described briefly, the control system 15 will function to either successively place the tool 10 in one or more of these positions or else cycle the tool between selected ones of these operating positions. These five operating positions are simply achieved by selectively moving suitable control switches. as schematically represented at 23 and 24, included in the surface portion of the system 15 to various switching. positions, as at 25-30, so as to selectively apply power to different conductors 31-37 in the cable 14.

bodiment of the entire downholeportion of the control system 15 as well as the tool-anchoring means 19, the

' fluid-admitting means and the fluid-collecting chambers 21 and 22 of the tool 10 are schematically illustrated with their several elements or components depicted as they will respectively be arranged when the new and improved tool 10 is fully retracted and the switches 23 and 24 are in their first or off operating positions 25. in the preferred embodiment of the selectively-extendible tool-anchoring means 19 schematically illustrated in FIG. 2A, an upright wallengaging anchor member 38 along the rear of the tool body 18 is coupled in a typical fashion to a longitudinally-spaced pair of laterally-movable piston actuators 39 and 40 of a typical design mounted transversely on the tool body 18. As will be subsequently explained, the lateral extension and retraction of the wall-engaging member 38 in relation to the rear of the tool body 18 is controlled by the control system 15 which is operatively arranged to selectively admit and discharge a pressured hydraulic fluid to and from the piston actuators 39 and 40.

Thefluid-admitting means 20 employed with the new and improved tool 10 are cooperatively arranged for sealing-off or isolating selected portions of the wall of the borehole 11; and, once a selected portion of the borehole wall is'packed-off or isolated'from the well bore fluids, establishing pressure or fluid communication with the adjacent earth formations in preparation for practicing the present invention. As depicted 'in FIG. 2A, the fluid-admitting means 20 preferably in- I elude an annular elastomeric sealing pad 41 mounted on the forward face of an upright support member of plate 42 that is coupled to a longitudinally-spaced pair of forwardly-movable piston actuators 43 and 44 respectively arranged transversely on the tool body 18 for moving the sealing pad laterally in relation to the forward side of the tool body. Accordingly, as the control system 15 selectively supplies a pressured hydraulic fluid to the piston actuators 43 and 44, the sealing pad 41 will be moved laterally between a retracted position adjacent to the forward side of the tool body 18 and an advanced or forwardly-extended position.

' Turning now to FIGS. 2A and 2B, the preferred emsealing pad into sealing engagement with the adjacent wall of the borehole 11 and anchoring the tool 10 each time the piston actuators 39, 40, 43 and 44 are extended. It will, however, be appreciated that the wallengaging member 38 as well as its-piston actuators 39 and 40 would not be needed if the effective stroke of the piston actuators 43 and 44 would be sufficient for assuring that the sealing member 41 can be extended into firm sealing engagement with one wall of the borehole 11 with the rear of the tool body 18 securely anchored against the opposite wall of the borehole. Conversely, the piston actuators 43 and 44 could be sim'ilarly omitted where the extension of the wall-engaging member 38 alone would be effective for moving the other side of the tool body 18 forwardly toward one wall of the borehole 1 l to place the sealing pad 41 into firm sealing engagement therewith. However, in the preferred embodiment of the formation-testing tool 10, both the tool-anchoring means 19 and the fluidadmitting means 20. are made selectively extendible to enable the tool to be operated in boreholesof substantial diameter. This preferred design of the tool 10, of course, results in the overall stroke of the piston actuators 39 and 40 and the piston actuators 43 and 44 being kept to a minimum so as to reduce the overall diameter of the tool body 18.

To conduct connate fluids into the new and improved tool 10, the fluid-admitting means 20 further include an enlarged tubular member 45 having an open forward portion coaxially disposed within the sealing pad 41 and a closed rear portion which is slidably mounted within a larger tubular member 46 secured to the rear face of the plate 42 and extended rearwardly therefrom. By arranging the nose of the tubular fluidadmitting member 45 to normally protrude a short distance ahead of the forward face of the sealing pad 41, extension of the fluid-admitting means 20 will engage theforward end of the fluid-admitting member with the adjacent surface of the wall of the borehole 11 just before the annular sealing pad is also forced thereagainst for isolating that portion of the borehole wall as well as the nose of the fluid-admitting member from the well bore fluids. To selectively move the tubular fluidadmitting member 45 in relation to the enlarged outer 1 member 46, the smaller tubular member is slidably disposed within the outer tubular member and fluidly sealed in relation thereto as by sealing members47 and 48 on inwardly-enlarged end portions 49 and 50 of the outer member and a sealing member 51 on an enlarged-diameter intermediate portion 52 of the inner member.

Accordingly, it will be appreciated that by virtue of the sealing members 47, 48 and 51, enclosed piston chambers 53 and 54 are defined within the outer tubular member 46 and on opposite sides of the outwardlyenlarged portion 52 of the inner tubular member 45 which, of course, functions as a piston member. Thus, by increasing the hydraulic pressure in the rearward chamber 53, the fluid-admitting member 45 will be moved forwardly in relation to the outer member 46 as well as to the sealing pad 41. Conversely, upon the application of an increased hydraulic pressure to the forward piston chamber 54, the fluid-admitting member 45 will be retracted in relation to the outer member 46 and the sealing pad 41.

Pressure or fluid communication with the fluidadmitting means is controlled by means such as a generally-cylindrical valve member 55 which is coaxially disposed within the fluid-admitting member 45 and cooperatively arranged for axial movement therein between a retracted or open position and the illustrated advanced or closed position where the enlarged forward end 56 of the valve member is substantially, if not altogether, sealingly engaged with the forwardmost interior portion of the fluid-admitting member. To sup port the valve member 55, the rearward portion of the valve member is axially hollowed, as at 57, and coaxially disposed over a tubular member 58 projecting forwardly from the transverse wall 59 closing the rear end of the fluid-admitting member 45. The axial bore 57 is reduced and extended forwardly along the valve member 55 to a termination with one or more transverse fluid passages 60 in the forward portion of the valve member just behind its enlarged head 56.

To provide piston means for selectively moving the valve member 55 in relation to the fluid-admitting member 45, the rearward portion of the valve member is enlarged, as at 61, and outer and inner sealing members 62 and 63 are coaxially disposed thereon and respectively sealingly engaged with the interior of the fluid-admitting memberand the exterior of the forwardly-extending tubular member 58. A sealing member 64 mounted around'the intermediate portion of the valve member 55 and sealingly engaged with the interior wall of the adjacent portion of the fluid-admitting member 45 fluidly seals the valve member in relation to the fluid-admitting member. Accordingly, it will be appreciated that by increasing the hydraulic pressure in the enlarged piston chamber 65 defined to the rear of the enlarged valve portion 61 which serves as a piston member, the valve member 55 will be moved forwardly in relation to the fluid-admitting member 45. Con versely, upon application of an increased hydraulic pressure to the forward piston chamber 66 defined between the sealing members 62 and 64, the valve member 55 will be moved rearwardly along the forwardlyprojecting tubular member 58 so as to retract the valve member in relation to the fluid-admitting member 45.

Those skilled in the art will, of course, appreciate that many earth formations, as at 12, are relatively unconsolidated and are, therefore, readily eroded by the withdrawal of connate fluids. Thus, to prevent any significant erosion of such unconsolidated formation materials. the fluid-admitting member 45 is arranged to define an internal annular space 67 and a flow passage 68 in the forward portion of the fluid-admitting member, and a tubular screen 69 with slits or apertures of suitable finenessis coaxially mounted around the annular space. In this manner, when the valve member 55 is retracted. formation fluids will be compelled to pass through the exposed forward portion of the screen 69 ahead of the enlarged head 56, into the annular space 67, and then through the fluid passage 60 into the fluid passage 57 and the tubular member 58. Thus, as the valve member 55 is retracted, should loose or unconsolidated formationmaterials be eroded from a formation as connate fluids are withdrawn therefrom, the materials will be stopped by the exposed portion of the screen 69 ahead of the enlarged head 56 of the valve 6 member thereby quickly forming a permeable barrier to prevent the continued erosion of loose formation materials once the valve member halts.

A sample or flow line 70 is cooperatively arranged in the formation testing tool 10 and has one end coupled, as by a flexible conduit 71, to the fluid-admitting means 20 and its other end terminated in a pair of branch conduits 72 and 73 respectively coupled to the fluidcollecting chambers 21 and 22. To control the communication between the fluid-admitting means 20 and the fluid-collecting chambers'2l and 22, normally-closed flow-control valves 74-76 of a similar or identical design are arranged respectively in the flow line 70 and in the branch conduits 72 and 73 leading to the sample chambers. For reasons which will subsequently be described in greater detail, a normally-open control valve 77 which is similar to the normally-closed control valves 74-76 is cooperatively arranged in a branch conduit 78 for selectively controlling communication between the well bore fluids exterior of the tool 10 and the upper portion of the flow line 70 extending between the flow-line control valve 74 and the fluid-admitting means 20.

As illsutrated, the control valve 77 is comprised of a valve body 79 cooperatively carrying a typical piston actuator 80 which is normally biased to an elevated position by a spring 81 of a predetermined strength. A valve member 82 coupled to the piston actuator 80 is cooperatively arranged for blocking fluid communication between the inlet and outlet fluid ports of the control valve whenever the valve member is moved to its lower position. The control valves 74-76 are similar to the control valve 77 except that a spring of selected strength is respectively arranged in each for normally biasing each of these valve members to a closed position.

In keeping with the principles of the present invention, a branch conduit 83 is coupled to the flow line 70 at a convenient location between the sample chamber control valves 75 and 76 and the flow-line control valve 74, with this branch conduit being terminated at selectively-operable expansion means such as an expansion chamber 84 of a predetermined volume carrying a reduced-diameter displacement piston 85 which is arranged to be moved between selected upper and lower positions in the chamber by a typical piston actuator 86. For purposes of better achieving the objects of the present invention, the volume which can be displaced by moving the piston 85 in the chamber 84 is selected to be as large as possible in relation to the combined volumes of the branch conduit 83 and that porelevated or upper position, the combined volume of whatever fluids that are then contained in the branch conduit 83 as well as in that portion of the flow line 70 between the flow-line control valve 74 and the sample chamber control valves 75 and 76 will be significantly increased. The significance of this will subsequently be explained by reference to FIGS. 6A-6D.

As best seen in FIG. 2A, the preferred embodiment of the control system 15 further includes a pump 87 that is coupled to a driving motor 88 and cooperatively arranged for pumping a suitable hydraulic fluid such as oil or the like from a reservoir 89 into a discharge or outlet line 90. Since thetool 10 is to be operated in well bores, as at 11, which typically contain dirty and usually corrosive fluids, the reservoir 89 is preferably arranged to totally immerse thepump 87 and the motor 88 in the clean hydraulic fluid. Inasmuch as the formation-testing tool 10 must operate at extreme depths, the

hydrostatic pressure at whatever depth the tool is then situated. A spring 93 is arranged to act on the piston 92 .for maintaining the pressure of the hydraulic fluid in thereservoir 8 9 at an increased level slightly above the well bore hydrostatic pressure so as to at least minimize the influx of well bore fluids into the reservoir. In addition to isolating the hydraulic fluid in the reservoir 89, thepiston 92 will also be free to move as required to accommodate volumetric changes in the hydraulic fluid which may occur under different well bore conditions. One or more inlets, as at 94 and 95, are provided for returning hydraulic fluid from the control system to the reservoir 89 during the operation of the tool 10.

trol switch 23 at the surface is selectively positioned;

and a typical check valve 100 is arranged in the set line 96 downstream of the control valve 98 for preventing the reverse flow of the hydraulic fluid whenever the pressure in the set line is greater than that then existing in the fluid outlet line 90. Typical pressure switches 101-103 are cooperatively arranged in the set and retract lines 96 and 97 for selectively discontinuing operation of the pump 87 whenever the pressure of the hydraulic fluid in either of these lines reaches a desired operating pressure and then restarting the pump whenever the pressure drops below this value so as .to maintain the line pressure within a selected operating range.

Since it is preferred that the pump 87 be a positivedisplacement type to achieve a rapid predictable rise in the operating pressures in the set and retract lines 96 and 97 in a minimum length of time, the control system 15 also provides for temporarily opening the outlet line 90 until the motor 88 has reached its rated operating speed. Accordingly,'the control system 15 is cooperatively arranged so that each time the pump 87 is to be started, the control valve 99 (if it is not already open) as well as a third normally-closed solenoid-actuated valve 104 will be temporarily opened to bypass hydraulic fluid directly from the output line 90 to the reservoir 89 by way of the return line 94. Once the motor 88 has reached operating speed, the bypass valve 104 will, of course, be reclosed and either the set line control valve 98 or the retract line control valve 99 will be selectively opened as required for that particular operational phase of the tool 10. It should be noted that during those times that the retract line control valve 99 and the fluid-bypass valve 104 are opened to allow the motor 88 to reach its operating speed, the check valve 100 will function to prevent the reverse flow of hydrau lic fluid from the set line 96 when the set line control valve 98 is open.

Accordingly, it will be appreciated that the control system 15 cooperates for selectively supplying pressured hydraulic fluid to the set and retract lines 96 and I 97. Since the pressure switches 101 and 102 respec tively function only to limit the pressures in the set and retract lines to a selected maximum pressure range commensurate with the rating of the pump 87, the new and improved control system 15 is further arranged to cooperatively regulate the pressure of the hydraulic fluid which is being supplied at various times to selected portions of the system. Although this regulation can be accomplished in different manners, it is preferred to employ a. number of pressure-actuated con- 7 trol valves such as shown schematically at 105-108 in FIGS. 2A and 2B. As shown in FIG. 2A, the control valve 105, for example, includes a valve body 109 having a valve seat 110 coaxially arranged therein between inlet and outlet fluid ports. .The upper portion of the valve body 109 is enlarged to provide a piston cylinder 111 carrying an actuating piston 112 in coincidental alignment with the valve seat 110. A spring 113 of a predetermined strength is arranged for normally urging the actuation piston l 12 toward the valve seat 110 and a control port 114 is provided for admitting hydraulic fluid into the cylinder 111 at a sufficient pressure to overcome the force of this spring whenever the piston is to be selectively moved away from the valve seat. Since the control system 15 operates at pressures no less than the hydrostatic pressure of the well bore fluids, a relief port 115 is provided in the valve body 109 for communicating the space in the cylinder 11 1 above the actuating piston 112 with the reservoir 89. A valve member 1 16 complementally shaped for seating engagement with the valve seat 110 is cooperatively coupled to the actuating piston 112 as by an upright stem 117 which is slidably disposed in an axial bore 118 in i. the piston. A spring 119 of selected strength is disposed in the axial bore 118 for normally urging the valve member 116 into seating engagement with the valve seat 110.

Accordingly, in its operating position depicted in FIG. 2A, the control valve 105 (as well as the valve 106) will simply function as a normally-closed check valve. That is to say, in this operating position, hydraulic fluid can flow only in a reverse direction whenever the pressure at the valve outlet is sufficiently greater than the inlet pressure to elevate thevalve member 116 from the valve seat 110 against the predetermined closing force imposed by the spring 119. On the other hand, when sufficient fluid pressure is applied to the control port 1 14 for elevating the actuating piston, op-

posed shoulders, as at 120, on the stem 117 and the pisthat the control valve 107 (as well as the valve 108) is similar to the control valve except that in the firstmentioned control valve, the valve member 121 is preferably rigidly coupled to its associated actuating piston 122. Thus, the control valve 107 (as well as the valve 108) has no alternate checking action allowing reverse flow and is simply a normally-closed pressure-actuated valve selectively controlling fluid communication between its inlet and outlet ports. Hereagain, the hydraulic pressure at which the control valve 107 (as well as the valve 108) is to selectively open is governed by the predetermined strength of the spring 123 normally biasing the valve member 121 to its closed position.

The set line 96 downstream of the check valve 100 is comprised of a low-pressure section 124 having one branch 125 coupled to the fluid inlet of the control valve 107 and another branch 126 which is coupled to the fluid inlet of the control valve 105 to selectively supply hydraulic fluid to a high-pressure section 127 of the set line which is itself terminated at the fluid inlet of the control valve 108. To regulate the supply of hy draulic fluid from the low-pressure section 124 to the high-pressure section 127 of the set line 96, a pressurecommunicating line 128 is coupled between the lowpressure section and the control port 114 of the control valve 105. Accordingly, so long as the pressure of the hydraulic fluid in the low-pressure section of the set line 96 remains below the predetermined actuating pressure required to open the control valve 105, the high-pressure section 127 will be isolated from the lowpressure section 124. Conversely, once the hydraulic pressure in the low-pressure line 124 reaches the predetermined actuating pressure of the valve 105, the control valve will open to admit the hydraulic fluid into the high-pressure line 127.

The control valves 107 and 108 are respectively arranged to selectively communicate the low-pressure and high-pressure sections 124 and 127 of the set line 96 with the fluid reservoir 89. To accomplish this, the control ports of the two control valves 107 and 108 are each connected to the retract line 97 by suitable pressure-communicating lines 129 and 130. Thus, whenever the pressure in the retract line 97 reaches their respective predetermined actuating levels, the control valves 107 and 108 will be respectively opened to selectively communicate the two sections 124 and 127 of the set line 96 with the reservoir 89 by way of the return line 94 coupled to the respective outlets of the two control valves.

As previously mentioned, in FlGS. 2A and 2B the tool 10 and the sub-surface portion of the control system are depicted as their several components will appear when the tool is retracted. At this point, the wall-engaging member 38 and the sealing pad 41 are respectively retracted against the tool body 18 to facilitate passage of the tool 10 into the borehole 11. To prepare the tool 10 for lowering into the borehole 11, the switches 23 and 24 are moved to their second orinitialization positions 26. At this point, the hydraulic pump 87 is started to raise the pressure in the retract line 97 to a selected maximum to be certain that the pad 41 and the wall-engaging member 38 are fully retracted. As previously mentioned, the control valves 99 and 104 will be momentarily opened when the pump 87 is started until the pump motor 88 has reached its operating speed. At this time also, the control valve 77 is open and that portion of the flow line 70 between the closed flow-line control valve 74 and the fluid-admitting means 24 will be filled with well bore fluids at the hydrostatic pressure at the depths at which the tool 10 is then situated.

Whenthe tool 10 is at a selected operating depth, the switches 23 and 24 are advanced to their third positions 27. Then, once the pump 87 has reached its rated operating speed. the hydraulic pressure in the output line 90 will rapidly rise to its selected maximum operating pressure as determined by the maximum or off" setting of the pressure switch 101. As the pressure progressively rises, the control system 15 will successively function at selected intermediate pressure levels for sequentially operating the several control valves 105-108 as described fully in the aforementioned copending application, Ser. No. 313,235.

Turning now to FIG. 3, selected portions of the control system 15 and various components of the tool 10 are schematically represented to illustrate the operation of the tool at about the time that the pressure in the hydraulic output line reaches its lowermost intermediate pressure level. To facilitate an understanding of the operation of the tool 10 and the control system 15 at this point in its operating cycle, only those components which are then operating are shown in FIG. 3.

At this time, since the control switch 23 (FIG. 1) is in its third position 27, the solenoid valves 98 and 104 will be open; and, since the hydraulic pressure in the set line 96 has not yet reached the upper pressure limit as determined by the pressure switch 101, the pump motor 88 will be operating. Since the control valve 105 (not shown in FIG. 3) is closed, the high-pressure section 127 of the set line 96 will still be isolated from the low-pressure section 124. Simultaneously, the hydraulic fluid contained in the forward pressure chambers of the piston actuators 39, 40, 43 and 44 will be displaced (as shown by the arrows as at 131) to the retract line 97 and returned to the reservoir 89 by way of the open solenoid valve 104. These actions will, or course, cause the wall-engaging member 38 as well as the sealing pad 41 to be respectively extended in opposite lateral directions until each has movedinto firm engagement with the opposite sides of the borehole ll.

lt-will be noticed in FIG. 3 that hydraulic fluid will be admitted by way of branch hydraulic lines 132 and 133 to the enclosed annular chamber 53 to the rear of the enlarged-diameter portion 52 of the fluid-admitting member 45. At the same time, hydraulic fluid from the piston chamber 54 ahead of the enlarged-diameter portion 52 will be discharged by way of branch hydraulic lines 134 and 135 to the retract line 97 for progressively moving the'fluid-admitting member 45 forwardly in relation to the sealing member 41 until the nose of the fluid-admitting member contacts the wall of the borehole 11. The nose of the fluid-admitting member 45 will, therefore, engage the wall of the borehole 11 and then halt as the sealing pad 41 is urged forwardly in relation to the now-halted fluid-admitting member until the pad is sealingly engaged with the borehole wall for packing-off or isolatingthe isolated wall portion from the well'bore fluids. In this manner, mudcake immediately ahead of the fluid-admitting member 45 willv be displaced radially away from the nose of the fluidadmitting member so as to-minimize the quantity of unwanted mudcake which will subsequently be admitted into the fluid-admitting means 20 during the practice of the present invention. Those skilled in the art will appreciate the significance of this arrangement.

It should also be noted that although the pressured hydraulic fluid is also admitted at this time into the for ward piston chamber 66 between the sealing members 62 and 64 on the valve member 55, the valve member is temporarily prevented from moving rearwardly in relation to the inner and outer tubular members 45 and 46 inasmuch as the control valve 106 (not shown in FIG. 3) is still closed thereby initially trapping the hy- 1 1 draulic fluid in the rearward piston chamber 65 to the rear of the valve member. The significance ofthis delay in the retraction of the valve member 55 will be subse- V quently explained.

As illustrated in FIG. 3, the hydraulic fluid in the lowpressure section-124 of the set line 96 will also be directed by way of a branch hydraulic line 136 to the piston actuator 86. This will, of course, result in the displacement piston 85 being elevated as the hydraulic fluid from the piston actuator is returned to the retract line 97 by way of a branch hydraulic conduit 137. As will be appreciated, elevation of the displacement piston 85 in the expansion chamber 84 will be effective for significantly decreasing the pressure initially existing in the isolated portions of the branch line 83 and the flow line 70 between the still-closed flow-line control valve 74 and the still-closed chamber control valves 75 and 76 (not shown in FIG. 3). The part that this pressure reduction plays in the practice of the present invention will be subsequently explained.

-Once the wall-engaging member 38, the sealing pad 41 and the fluid-admitting member 45 have respectively reached their extended position as illustrated in FIG, 3, it will be appreciated that the hydraulic pressure delivered by the pump 87 will again rise. Then, once the pressure in the output line 90 has reached its second intermediate level of operating pressure, the

control valve 106 will open in response to this pressure level to now discharge the hydraulic fluid previously trapped in the piston chamber 65 to the rear of the valve member 55 back to the reservoir 89.

As illustrated in FIG. 4, when the control valve 106 opens, the hydraulic fluid will be displaced from the rearward piston chamber 65 by way of branch hydraulic lines 138 and 139 and 135 to the retract line 97 as pressured hydraulic fluid from the set line 96 surges into the piston chamber 66 ahead of the enlargeddiameter portion 61 of the valve member 55. This will, of course, cooperate to rapidly drive the valve: member 55 rearwardly in relation to the now-advanced fluidpressure communication between the isolated portion of the earth formation 12 and the flow passages 57 and '60 in the valve member by way of the filter screen 69 as the branch line 83 leading to the pressure-reduction chamber 84. However, the flow-line pressureequalizing control valve 77 willstill be open at the time the control valve 106 opens to retract the valve member 55 as depicted in FIG. 4. Thus, as the valve member 55 progressively uncovers the filtering screen 69, well bore fluids at a pressure greater than that of any connate fluids which may be present in the isolated earth formation 12 will be introduced into the upper portion of the flow line 70 and, by way of the flexible conduit member 71, into the rearward end of the tubular member 58. As these high-pressure well bore fluids pass into the annular space 67 around the filtering screen 69, they will be forcibly discharged (as shown by the arrows 140) from the forward end of the fluid-admitting member 45 for washing away any plugging materials such as mudcake or the like which may have become deposited on the internal surface of the filtering screen admitting member for suddenly establishing fluid or here fluids for cleansing the filtering screen 69 of unwanted debris or the like before a sampling or testing operation is commenced.

It will be appreciated that once the several components of the formation-testing tool 10 and'the control system 15 have reached their respective positions as depicted in FIG. 4, the hydraulic pressure in the output line will again quickly increase to its next intermediate pressure level. Once the pump 87 has increased the hydraulic pressure in the output line 90 to this next predetermined intermediate pressure level, the control valve will selectively open as depicted in FIG. 5. As seen there, opening of the control valve 105 will be effective for now supplying hydraulic fluid to the highpressure section 127 of the set line 96 and two branch conduits 141 and 142 connected-thereto for successively closing the control valve 77 and then rapidly opening the control valve 74.

In this manner, as depicted by the several arrows at 143 and 144, hydraulic fluid at a pressure representative of the intermediate operaing level will be supplied by way of a typical check valve 145 to the upper portion of the piston cylinder 146 of the normally-open control valve 77 as fluid is exhausted from the lower portion thereof by way of a conduit 147 coupled to the retract line 97. This will, of course, be effective for closing the valve member 82 so as to now block further communication between the flow line 70 and the well bore fluids exterior of the tool 10. Simultaneously, the hydraulic fluid will also be admitted into the lower portion of the piston cylinder 148 of the control valve 74. By arranging the biasing spring 81 for the normallyopen control valve 77 to be somewhat weaker than the biasing spring 149 for the normally-closed control valve 74, the second valve will be momentarily retained in its closed position until the first valve has had time to close. Thus, once the valve 77 closes, as the hydraulic fluid enters the lower portion of the piston chamber 148 of the control valve 74, the valve member 150 will be rapidly opened as hydraulic fluid is exhausted from the upper portion of the chamber through a typical check valve 151 and a branch return line 152 coupled to the retract line 97.

It will be appreciated, therefore, that with the tool 10 in the position depicted in FIGS. 5A and 5B, the flow line 70 is now isolated from the well bore fluids and is in communication with the isolated portion of the earth formation .12 by way of the flexible conduit 71 and the fluid-admitting means 20. It will also be recalled from the preceding discussion of FIG. 3 that in keeping with the objects of the present invention, the branch flow line 83 as well as the portion of the main flow line 70 between the flow-line control valve 74 and the sample chamber control valves 75 and 76 were previously expanded by the upward movement of the displacement piston 85 in the reduced-volume chamber 84. The pressure in this isolated volume will, of course, be about atmospheric pressure if not sub-atmospheric. Thus, upon the rapid opening of the flow-line control valve 74, the isolated portion of the earth formation 12 in communication with the fluid-admitting means 20 will be suddenly communicated with the reduced-pressure space represented by the previously-isolated portions of the flow line 70 and the branch conduit 83.

Accordingly, in keeping with the principles of the present invention, should there be any producible connate fluids in the isolated earth formation 12, the formation pressure will be effective for rapidly displacing these connate fluids by way of the fluid-admitting means 20 into the flow line until such time that the lower portion of the flowline 70 and the branch conduit 83 are filled and pressure equilibrium is again established in the entire flow line. As will subsequently be explained in greater detail, the pressure of the inrushing connate fluids will'typically momentarily drop to about atmospheric pressure and then quickly rise as the previously-isolated volume rapidly fills. By arranging a typical pressure-measuring transducer 153 in the flow line 70, one or more pressure measurements representative of the characteristics of the connate fluids and the formation 12 may be transmitted to the surface by a conductor 154 and, if desired, recording on the recording apparatus 16 (FIG. 1). The pressure measurements provided by the transducer 153 will, of course,

that by virtue of the purgingaction previously provided by the outflowing well bore fluids, there is a reasonable assurance that the filtering screen 69 will be cleared of plugging materials such as mudcake or formation materials that may otherwise plug the fluid-admitting-means 20.

The measurements provided by the pressure transducer 153 at this time will,'among other things, indicate whether'the sealing pad 41 has, in fact, established complete sealing engagement with the earth formation l2 inasmuch as the expected formation pressures will be recognizably lower than the hydrostatic pressure of thewell bore fluids at the particular depth which the tool is then situated. This ability to determine the effectiveness of the sealing engagement will, of course, allow the operator to retract the wall-engaging member 38 and the sealing pad 41 without having to unwittingly or needlessly continue the remainder of the complete operating sequence.

Assuming, however, that the pressure measurements provided by the pressure transducer 153 show that the sealing pad 41 is firmly seated, the operator may leave the formation-testing tool 10 in the position shown in FIGS. 5A and 58 as long as it is desired to observe as well as record the pressure measurements. As a result, in the practice of the present invention, the operator can also determine such things as the time required for the formation pressure to reach equilibrium as well as the rate of increase and thereby obtain valuable information indicative of various characteristics of the earth formation 12 such as permeability and porosity. Moreover, with the new and improved tool 10, the operator can readily determine if collection of a fluid sample is warranted.

It should be noted that should the formation 12 be relatively unconsolidated, the rapid opening of the valve 74 will cause any mudcake trapped in the forward end of the fluid-admitting member 45 to be impelled into the fluid-admitting member and come to rest against the forward end 56 of the valve member 55 and allow only those loose formation materials displaced by the advancement of the fluid-admitting member into the formation to rush into the fluid-admitting member. It should be noted that the fluid-admitting member 45 can advance into the formation 12 only by displacing loose formation materials; and, since the space opened within the forward end of the fluid-admitting member by the rearward displacement of the valve member 55 is the only place into which the loose formation materials can enter, further erosion of the formation materials will be halted once the fluid-admitting member has filled with loose formation materials.

On the other hand, should the formation 12 be relatively well-compacted, the advancement of the fluidadmitting member 45 will the relatively slight with its nose making little or no penetration into the isolated earth formation. It will, of course, be appreciated that the nose of the fluid-admitting member 45 will be urged outwardly with sufficient force to at least penetrate the mudcake which typically lines the borehole walls adjacent to permeable earth formations. In this situation,

however, the forward movement of the fluid-admitting member will be unrelated to the rearward movement of the valve member as it progressively uncovers the filtering screen 69. The rapid opening of the valve 74 will, however, still be effective for drawing the trapped mudcake into the fluid-admitting member 45 to the rear of the screen 69. This, of course, will leave the screen 69 clear of possibly-plugging materials. There will, of course, often be little foreign matterto possibly plug the screen 69 where the formation 12 is well' consolidated. Thus, as connate fluids are produced, the mudcake previously trapped in the fluidadmitting member 45 may well be washed on through the filtering screen 69. Generally, this will pose no particular problem such as will occur with soft formations since with these s'oft formations it is the comingling of the mudcake with loose formation most likely plug the screen 69.

Once the several components of the tool 10 and the control system 15 have moved to their respective positionsshown in FIGS. 5A and 5B, the hydraulic pressure will againrise until such time that the set line pressure switch 101 operates to halt the hydraulic pump 87. Inasmuch as the pressure switch 101 has a selected operating range, in the typical situation the pump 87 will be halted shortly after the control valve 77 closes and the control valve 74 opens. At this point in the operating cycle of the tool 10, once a sufficient number of pressure measurements have been obtained, a decision can be made whether it is advisable to obtain one or more samples of the producible connate fluids present in the earth formation 12. If such samples are not desired, the operator can simply operate the control switches '23 and 24 for retracting the wall-engaging member 38 as well as the sealing pad 41 without further ado.

On the other hand, should a fluid sample be desired, the control switches 23 and 24 (FIG. 1) are advanced to their next or so-called saimple 28 to open, for example, a solenoid valve 155 for coupling pressured hydraulic fluid from the high-pressure section 127 of the set line 96 to the piston actuator 156 of the sample chamber control valve 75. This will, of course, be effective for opening the control valve 75 to admit connate fluids through the flow line and the branch conduit 72 into the sample chamber 21. 1f desired,'a chamber particles that will v their so-called sample-trapping" positions 29, the

pump 87 will again be restrated. Once the pump 87 has reached operating speed, it will commence to operate much in the same manner as previously described and the hydraulic pressure in the output line 90 will again begin rising with momentary halts at various intermediate pressure levels.

2 Accordingly, when the control switches 23 and 24 have been placed in their sample trapping positions 29, the solenoid valve 99 will open to admit hydraulic fluid into the retract line 97. By means of the electrical conductor 1030, however, the pressure switch 103 is enabled and the pressure switch 102 is disabled so that in this position of the control switches 23 and24 the maximum operating pressure which thepump 87 can initially reach is limited to the pressure at the operating pressure level determined by the pressure switch 103.

Thus, by arranging the control valve 108 to open inresponse to a hydraulic pressure corresponding to this predetermined pressurelevel, hydraulic fluid in the high-pressure section 127 of the set line 96 will be returned to the reservoir 89 by means of the return line 94. As the hydraulic fluid in the high-pressure section 127 returns to the reservoir 89, the pressure in this por tion of the set line 96 will be rapidly decreased to close the control valve 105 once the pressure in the line is insufficient to hold the valve open. Once the control valve 105 closes, the.pressure remaining in the lowpressure section 124 of the set line 96 will remain at a reduced pressure which is nevertheless effective for retaining the wall-engaging member 38 and the sealing pad 41 fully extended.

' As the hydraulic fluid is discharged from'the lower portion of the piston actuator 156 by way of the stillopen solenoid valve 155 and fluid from the retract line 97 enters the upper portion of the actuator by way of a branch line-161, the chamber control valve 75 will close to trap the sample of connate fluids which is then present in. the sample chamber 21. Similarly, should there also be a fluid sample in the other sample chamber 22, the control valve 76 can also bereadily closed by operating the switch 157 to reopen the solenoid valve 160. Closure of the control valve 75 (as well as the valve 76) will, of course, be effective for trapping any fluid samples collected in one or the other or both of the sample chambers 21 and 22.

Once the control valve 75 (and, if necessary, the control valve 76) has been reclosed, the control switches 23 and 24 are moved to their next or so-called retract switching positions 30 for initiating the simultaneous retraction of the wall-engaging member 38 and the sealing pad 41. In this final position of the control switch 24, the pressure switch 103 is again rendered inoperative and the pressure switch 102 is enabled so as -to now permit the hydraulic pump 87 to be operated at full rated capacity for attaining hydraulic pressures greater than the first intermediate operating level in the retract cycle. Once the pressure switch 103 has again been disabled, the pressureswitch 102 will now function to operate the pump 87 so that the pressure will now'quickly rise until it reaches the next operating level.

At this point, hydraulic fluid will be supplied through the retract line 97 and the branch hydraulic line 147 for reopening the pressure-equalizing control valve 77 to admit well bore fluids into the flow line 70. Opening of the pressure-equalizing valve 77 will admit well bore fluids into the isolated space defined by the sealing pad 41 so asto equalize the pressure differential existing across the pad. Hydraulic fluid displaced from the upper portion of the piston chamber 146 of the control valve 77 will be discharged through a typical relief valve 161 which is arranged to open only in response to pressures equal or greater than that of this present operating level. The hydraulic fluid displaced from the piston chamber 146 through the relief valve 161 will be returned to the reservoir 89 by way of the branch hydraulic line 141, the high-pressure section 127 of the set line 96, the still-open control valve 108, and the return line 94.

When the hydraulic pressure in the output line 90 has either reached the next operating level or, if desired, a still-higher level, pressured hydraulic fluid in the retract line 97 will reopen the control valve 107 to communicate the low-pressure section 124 of the set line 96 with the reservoir 89. When this occurs, hydraulic fluid in the retract line will be admitted to the retract side of the several piston actuators 39, 40, 43 and 44. Similarly, the pressured hydraulic fluid will also be admitted into the annular space 54 in front of the enlargeddiameter piston portion 52 for retracting the fluidadmitting member 45 as well as into the annular space 66 for returning the valve member 55 to its forward position. The hydraulic fluid exhausted from the several piston actuators 39, 40, 43 and 44 as well as the piston chambers 54 and 56 will be returned directly to the reservoir 89 by way of the high-pressure section 124 of the set line 96 and the control valve 107. This action will, of course, retract the wall-engaging member 38 as well as the sealing pad 41 against the tool body 18 to permit the tool 10 to be either repositioned in the well bore 11 or returned to the surface .if no further testing is desired. I

it should be noted that although there is an operating pressure applied to the upper portion of the piston cylinder 148 for the flow-line control valve 74 at the time that the control valve 77 is'reopened, a normally-closed relief valve 162 which is paralleled with the check valve 151 is held in a closed position until the increasing hydraulic pressure developed by the pump 87 exceeds the operating level used to retract the wall-engaging member 38 and the sealing pad 41. At this point in the operating sequence of the new and improved tool 10, the flow-line control valve 74 will be reclosed.

The pump 87 will, of course, continue to operate until such time that the hydraulic pressure in the output line 90 reaches the upper limit determined by the setting of the pressure switch 102. At some convenient 1 time thereafter, the control switches 23 and 24 are again returned to their initial or off positions 25 for halting further operation of the pump motor 88 as well as reopening the solenoid valve 104 to again communicate the retract line 97 with the fluid reservoir 89. This completes the operating cycle of the new and improved tool 10.

Referring again to FIGS. A and 513, it will be recognized that, in keeping with the objects of the present invention, once the new and improved tool is set adjacent to the formation 12, the opening of theflow-line control valve 74 will enable the operator to quickly determine whether a subsequent testing or sampling operation is warranted. There will, of course, be several possible situations which may occur and which may be readily recognized by practicing the present invention.

For example, in the ideal situation, it will be hoped that the formation, as at 12, which is being tested is a potentially-producible formation. When this is the case, by using the methods and apparatus of the present invention, the pressure measurements provided by the transducer 153 will typically vary in a manner as schematically depicted by the curve 163 FIG. 6A. As illustrated at 164, the visually-observed indications as well as the recorded chart provided by the apparatus 16 will be a measurement of the hydrostatic pressure (P,,) of the well bore fluids so long as the equalizing valve 77 is open, e.g., FIG. 4. This measurement will, of course, vary in relation to the depth of the tool 10 but will remain steady once the tool is anchored in position in the well bore 11.

As previously discussed with respect to FIG. 3, the operation of the displacement piston 85 will reduce the pressure in the lower portion of the flow line 70 to a pressure which is at least near if not less than atmospheric pressure. Thus, when the pressure-equalizing control valve 77 is closed and the flow-line control valve 74 is snapped open, the isolated portion of the formation 12 will be suddenly communicated with the lower portion of the flow line 70 and the expansion chamber 84. Since any connate fluids in the formation 12 will be at a substantial pressure (P;), there will be a a sudden influx of these high-pressure fluids into the reduced-pressure spacedefined by the lower portion of the flow line 70 and the now-expanded chamber 84.

Accordingly, depending upon the speed at which the valve 74 is opened, the pressure of the entering connate fluids will rapidly drop to a momentary level at or near atmospheric pressure as indicated by the portion 165 of the curve 163. Thereafter, as equilibrium is reestablished in the flow line 70, the pressure of the'fluids in the flow line will rise to the formation pressure (P in a manner as depicted at 166 on the .curve 163. Those skilled in the art will, of course, appreciate that the rate at which the pressure measurement indicated at 166 increases will be directly related to the potential productivity of the formation, as at 12, which is then being tested. In other words, if the formation being tested is relatively permeable and contains connate fluids at a significant formation pressure there will be a corresponding rapid increase in the pressure measurements provided by the transducer 153. On the other hand, should the formation being tested be relatively impermeable. the restoration of pressure equilibrium in the flow line 70 will be proportionally slowed as shown at 167 on the typical curve 168 depicted in FIG. 68.

There is. of course, always the possibility that the formation being tested is non-productive by either failing to contain connate fluids or being so impermeable that connate fluids therein cannot be moved into the well bore 11. When this situation is encountered, the resulting pressure measurements will be like those shown at 169 on the curve 170 in FIG. 6C. As illustrated there, upon opening of the valve 74, the pressure in the flow line 70 will drop to the low values shown at 169 and remain there since there are no producible connate fluids filling the voided spaces in the flow line and the expansion chamber 84.

It will be realized, therefore, that by practicing the methods of the present invention, the operator can quickly determine whether a formation which is being tested is fluid-bearing and is sufficiently permeable to warrant further investigation. Since the volume of the reduced-pressure space in the lower portion of the flow line 70 and the expansion chamber 84 is relatively small, restoration ofpressure equilibrium in the flow line after the valve 74 is opened will be relatively quick. Thus, the operator will not have a prolonged wait before a determination can be made whether a fluid sample should be obtained. Moreover, measurements of the formation pressure are similarly speeded.

Those skilled in the art will, therefore, appreciate that the measurements now obtained by practicing the present invention were wholly unattainable with prior techniques without at least attempting to collect a fluid sample. For example, as previously mentioned, formation-testing tools such as those disclosed in US Pat. No. 3,0! l,554 are incapable of reducing the pressure in the flow line until the sample chamber is opened. Similarly, even with formation-testing tools such as shown in US. Pat. No. 3,577,78l, there is simply a reduction of the pressure measurement from the hydrostatic pressure directly to the formation pressure. This response, of course, neither provides a representative indication of the potential productivity of the formation being tested nor gives the operator sufficient time to make a qualitative evaluation.

Although the usual situation will be that the new and improved tool 10 will be operated as previously described in detail for obtaining a series of pressure measurements and possibly one or two fluid samples, it is not at all uncommon for unexpected or unwanted conditions to occur which will hamper or prevent the successful completion of that particular testing or sampling operation. For example, as previously mentioned, it is quite often found that the sealing pad 41 has, for one reason or another,'failed to effect complete sealing engagement with the wall of the borehole ll. Obviously, this condition will absolutely preclude the securing of either formation pressure measurements or representative fluid samples since well bore fluids will simply enter the fluid-admitting means 20 should the testing or sampling operation be continued.

This condition will, of course, be readily apparent since the pressure transducer 153 initially indicates the hydrostatic pressure of the well bore fluids (FIG. 4). Thus, once the flow-line control valve 74 opens to rapidly communicate the reduced-pressure portion of the I flow line 70 with the fluid-admitting means 20 only one of two things can occur if the sealing pad 41 is not sealingly engaged. First of all,if the formation, as at 12, is relatively well-consolidated and the pressure in the flow line fails to drop and instead either remains at the same level or very quickly returns to that level, it will be known that the sealing pad 41 is not tightly sealed with the wall of the borehole l1 and that well bore fluids are entering the nose of the fluid-admitting member 45. This situation is graphically represented by scribed, the control switches 23 and 24 are simply skipped over the positions 28 and 29 and advanced directly to their switching positions at 30 without further ado. This will, of course, return the tool to its initial position (FlGS. 2A and 28) so that one or more attempts can be made after moving the tool slightly so as to hopefully shift it to a better position in relation to the formation as at 12. This will allow the operator to better determine whether the formation is in'fact not productive or if the fluid-admitting means 20 were merely plugged temporarily.

ln arranging the new and improved apparatus of the present invention, it should be noted that the expansion chamber 84 must be sized in greatly expand the volume of the space initially represented by the lowerportion of the flow line 70 and the branch conduit 83. As discussed above, the volume of the displacement chamber 84 must be at least sufficient to substantially reduce the pressure in the total isolated space. Preferably, the better arrangement is to strive for a pressure reduction to about atmospheric pressure or even lower for achieving a more-representative observation or record of the .pressurerise than would be possible with a smaller cally sufficient to achieve a satisfactory pressure reduction. As a practical matter, however, since well boreliquids often contain dissolved gases, it is preferred to make the available displacement volume of the expansion chamber 84 as large as possible to be certain of reducing the pressure in the lower portionof the flow line 70 to about atmospheric pressure even when the well bore fluids in the space have a considerable percentage of dissolved. or entrained gases. In one embodiment of.

the new and improved tool 10, excellent results have been achieved by making the displacement volume of the piston 85 and chamber 84 about equal to the combined volumes of the branch conduit 83 and the lower portion of the flow line 70. This, of course, results in doubling ofthe enclosed space in the lower portion of the flow line 70 and the branch conduits 83 when the piston 85 is moved to its elevated position. Accordingly, it will be recognized that by virtue of the new and improved cooperative arrangement of the tool 10 with the control valve 74 and the expansion chamber 84,

one or more testing or sampling operations can be conducted without undue loss of time should the fluidadmitting means 20 not be in isolated communication with a selected formation or if the formation is found to have little or no production capability.

While only a particular embodiment of the present and one mode of practicing the invention have been shown and described, it is apparent that changes and modifications may be made without departing from this invention in its broader aspects; and, therefore, the aim in the appended claims is to cover all such changes and modifications as fall within the true spirit and scope of this invention.

What is claimed is:

1. A method for determining one or more characteristics of earth formations traversed by a well bore and comprising the steps of:

isolating a wall surface of said well bore adjacent to an earth formation believed to contain producible connate fluids from well bore fluids;

expanding the volume of an enclosed test chamber for reducing the pressure in said test chamber to a pressure less than the formation pressure of said earth formation; after said test chamber is expanded, communicating said expanded test chamber with said isolated wall surface at a speed sufficient to quickly induct a sample of producible connate fluids from said earth fomiation into said expanded test chamber for momentarily reducing the pressure of said connate fluid sample below said formation pressure;

monitoring the pressure in said expanded test chamber for obtaining a series of pressure measurements indicative of at least one characteristic of said earth formation; and, thereafter,

reducing the volume of said enclosed test chamber for expelling said connate fluid sample from said enclosed test chamber into said well bore.

2. The method of claim 1 further including the addi tional stepof:

recording said pressure measurements for producing a record representative of the production characteristics of said connate fluids from said earth formation;

3. The method of claim 1 further including the additional step of:

after the pressure-monitoring step, communicating said isolated wall surface with an enclosed sample chamber for obtaining another sample of producible connate fluids from said earth formation while said wall surface is still isolated.

4. The method of claim 1 wherein said test chamber is expanded until the reduced pressure therein is about atmospheric pressure. I

5. The method of claim 1 further including the additional steps of:. I

' re-expanding said enclosed test chamber for again reducing the pressure therein to a pressure less than said formation pressure;

after said test chamber is re-expanded, communicating said re expanded test chamber with said isolated wall surface at a speed sufficient to quickly induct a second sample of producible connate fluids from said earth formation into said re-expanded test chamber for momentarily reducing the pressure of said second sample below said formation pressure;

monitoring the pressure in said re-expanded test chamber for obtaining a second series of pressure measurements indicative at least one characteristic of said earth formation; and, thereafter,

again reducing the volume of said enclosed test chamber for expelling said second sample from said enclosed test chamber into said well bore.

6. The method of claim further including the additional step of:

recording said second pressure measurements for producing a record representative of the production characteristics of said connate fluids from said earth formation.

7. The method of claim 5 further including the additional step of:

after the step of monitoring the pressure in said reexpanded test chamber, communicating said isolated wall surface with an enclosed sample chamber for obtaining another sample of producible connate fluids from said earth formation while said wall surface is still isolated.

8. The method of claim 5 wherein said test chamber is re-expanded until the reduced pressure therein is about atmospheric pressure.

9. A method for determining the production characteristics of earth formations traversed by a well bore and comprising the steps of:

placing fluid-admitting means coupled to a fluid passage with normally-closed valve means arranged therein into sealing engagement with a wall surface of said well bore adjacent to an earth formation believed to contain producible connate fluids for isolating said wall surface from fluids in said well bore and placing one end of said fluid passage into position for subsequently receiving connate fluids from said earth formation;

expanding the volume of an enclosed test chamber coupled to said fluid passage downstream of said passage end for reducing the pressure in said fluid passage and said test chamber to about atmospheric pressure;

after said test chamber is' expanded, opening said valve means at a speed sufficient to quickly induct a sample of producible connate fluids from said earth formation into said expanded test chamber for momentarily reducing the pressure of said connate fluid sample to about atmospheric pressure; and

monitoring the pressure in said expanded test chamber for obtaining a series of pressure measurements indicative of the production capabilities of said earth formation.

10. The method of claim 9 further including the additional step of:

recording said pressure measurements for obtaining a record representative of the pressure characteristics of said earth formation as connate fluids are produced therefrom.

ll. The method of claim 9 further including the additional step of:

after the pressure-monitoring step, coupling an enclosed sample chamber to said fluid passage for collecting another sample of connate fluids from said earth formation.

12. The method of claim 11 further including the additional steps of: 7

coupling an additional enclosed sample chamber to said fluid passage for collecting still-another sample of connate fluids from said earth formation.

into said re-expanded test chamber for momentarily reducing the pressure of said second sample to about atmospheric pressure; and re-monitoring the pressure in said re-expanded test chamber for obtaining a second series of pressure measurements indicative of the production capabilities of said earth formation. 14. The method of claim 13 further including the additional step of:

after obtaining said pressure measurements, coupling an enclosed sample chamber to said fluid passage for collecting another sample of connate fluids from said earth formation. 15. The method of claim 13 further including the additional steps of:

after obtaining said pressure measurements, reducing the volume of said test chamber again for expelling said second sample into said well bore; re-closing said valve means; and disengaging said fluid-admitting means from said wall surface. 16. The method of claim 9 further including the additional steps of: 4

after the pressure-monitoring step, coupling an enclosed sample chamber to said fluid passage for collecting another sample of connate fluids from said earth formation; reducing the volume of said test chamber for expelling said sample of connate fluids into said well bore; re-closing said valve means; re-expanding the volume of said test chamber for again reducing the pressure in said fluid passage and said test chamber to about atmospheric pressure;

disengaging said fluid-admitting means from said wall surface and placing said fluid-admitting means into sealing engagement with another wall surface of said well bore adjacent to another earth formation believed to contain producible connate fluids for isolating said other wall surface from said well bore fluids; 2 re-opening said valve means at a speed sufficient to quickly induct a second sample of producible connate fluids into said re-expanded test chamber for momentarily reducing the pressure of said second sample to about atmospheric pressure; and re-monitoring the pressure in said re-expanded test chamber for obtaining a second series of pressure measurements indicative of the production capabilities of said other earth formation. 17. The method of claim 16 further including the additional steps of:

18. The method of claim 16 further including the ad ditional step of:

after obtaining said second series of pressure measur ements, reducing the volume of said test chamher again for expelling said second sample into said well bore; r e-closing said valve means; and disengaging said fluid-admitting means from other wall surface. 19. A method for determining the production characteristics of earth formations traversed by a well bore and comprising the steps of:

placing fluid-admitting means including a fluid passage coupled by a filtering medium to an intermediate portion of a fluid-sampling member having a normally-closed forward end and a rearward portion into sealing engagement with a wall surface of said well bore adjacent to an earth formation be-. lieved to contain 'producible connate fluids for isolating said wall surface from fluids in said well bore and placing said closed end of said fluid-sampling member into position for subsequently receiving connate fluids from said earth formation; expanding the volume of an enclosed test chamber coupled to said fluid passage downstream of said filtering medium for reducing the pressure in said fluid passage and said test chamber to about atmosaid spheric pressure; I I after said test chamber is expanded, opening said closed end of said fluid-sampling member and coupling said test chamber to said fluid passage at a speed sufficient to quickly induct a filtered sample of producible connate fluids from said earth formation into said expanded test chamber for momentarily reducing the pressure of said connate fluid sample to about atmospheric pressure and displacing loose plugging materials from said wall surface into said rearward portion of said fluid-sampling member to the rear of said filtering medium; and

monitoring the pressure in said-expanded test chamber for obtaining a series of pressure measurements indicative of the production capabilities of said earth formation. 20. The method of claim 19 further including the additional step of:

recording said pressure measurements for obtaining a record representative of the pressure characteristics of said earth formation as connate fluids are produced therefrom. 21. The method of claim 19 further including the additional step of:

after the pressure-monitoring step, coupling an enclosed sample chamber to said fluid passage downstream of said filtering medium for collecting another filtered sample of connate fluids from said earth formation. 22. The method of claim 21 further including the additional steps of:

coupling an additional enclosed sample chamber to said fluid passage downstream of said filtering medium for collecting still another filtered sample of connate fluids from said earth formation.

23. The method of claim 19 further ditional steps of:

after the pressure-monitoring step, reducing the volume of said test chamber for expelling said sample of connate fluids into said well bore; uncoupling said test chamber from said fluid passage;

including the adre-closing said normally-closed forward end of said fluid-sampling member;

re-expanding the volume of said test chamber for again reducing the pressure in said fluid passage and said test chamber to about atmospheric pressure;

after said test chamber is re-expanded, re-opening said closed end of said fluid-sampling member and re-coupling said re-expanded test chamber to said fluid passage at a speed'sufficient to quickly induct a second filtered sample of producible connate flu ids into said re-expanded test chamber for momentarily reducing the pressure of said second sample to about atmospheric pressure and displacing additional loose plugging materials from said wall surface into said rearward portion of said fluidsamplin g member to the rear of said filtering medium; and g re-monitoring the pressure in said re-expanded test I chamber for obtaining a second series of pressure measurements indicative of the productioncapa: bilities of said earth formation. 7 24. The method of claim 23 further including the additional step of:

after obtaining said pressure measurements, coupling an enclosed sample chamber to said fluid passage downstream of said filtering medium for collecting another filtered sample of connate fluids from said earth formation. a 25. The method of claim 23 further including the additional steps of: 7

after obtaining said pressure measurements, reducing the volume of said test chamber again for expelling said second sample into said well bore; re-closing said normally-closed forward end of said fluid-sampling member; and disengaging said fluid-admitting means from said wall surface. 26. The method of claim 19 further including the additional steps of:

after the pressure-monitoring step, coupling an enclosed sample chamber to said fluid passage downstream of said filtering medium for collecting another filtered sample of connate fluids from said earth formation;

reducing the volume of said test chamber for expelling said sample of connate fluids into said well bore;

uncoupling said test chamber from said fluid passage;

re-closing said normally-closed forward end of said fluid-sampling member;

re-expanding the volume of said test chamber for again reducing the pressure in said fluid passage and said test chamber to about atmospheric pressure;

disengaging said fluid-admitting means from said wall surface and placing said fluid-admitting means into sealing engagement with another wall surface of said well bore adjacent to another earth formation I 

1. A method for determining one or more characteristics of earth formations traversed by a well bore and comprising the steps of: isolating a wall surface of said well bore adjacent to an earth formation believed to contain producible connate fluids from well bore fluids; expanding the volume of an enclosed test chamber for reducing the pressure in said test chamber to a pressure less than the formation pressure of said earth formation; after said test chamber is expanded, communicating said expanded test chamber with said isolated wall surface at a speed sufficient to quickly induct a sample of producible connate fluids from said earth formation into said expanded test chamber for momentarily reducing the pressure of said connate fluid sample below said formation pressure; monitoring the pressure in said expanded test chamber for obtaining a series of pressure measurements indicative of at least one characteristic of said earth formation; and, thereafter, reducing the volume of said enclosed test chamber for expelling said connate fluid sample from said enclosed test chamber into said well bore.
 2. The method of claim 1 further including the additional step of: recording said pressure measurements for producing a record representative of the production characteristics of said connate fluids from said earth formation.
 3. The method of claim 1 further including the additional step of: after the pressure-monitoring step, communicating said isolated wall surface with an enclosed sample chamber for obtaining another sample of producible connate fluids from said earth formation while said wall surface is still isolated.
 4. The method of claim 1 wherein said test chamber is expanded until the reduced pressure therein is about atmospheric pressure.
 5. The method of claim 1 further including the additional steps of: re-expanding said enclosed test chamber for again reducing the pressure therein to a pressure less than said formation pressure; after said test chamber is re-expanded, communicating said re-expanded test chamber with said isolated wall surface at a speed sufficient to quickly induct a second sample of producible connate fluids from said earth formation into said re-expanded test chamber for momentarily reducing the pressure of said second sample below said formation pressure; monitoring the pressure in said re-expanded test chamber for obtaining a second series of pressure measurements indicative at least one characteristic of said earth formation; and, thereafter, again reducing the volume of said enclosed test chamber for expelling said second sample from said enclosed test chamber into said well bore.
 6. The method of claim 5 further including the additional step of: recording said second pressure measurements for producing a record representative of the production characteristics of said connate fluids from said earth formation.
 7. The method of claim 5 further including the additional step of: after the step of monitoring the pressure in said re-expanded test chamber, communicating said isolated wall surface with an enclosed sample chamber for obtaining another sample of producible connate fluids from said earth formation while said wall surface is still isolated.
 8. The method of claim 5 wherein said test chamber is re-expanded until the reduced pressure therein is about atmospheric pressure.
 9. A method for determining the production characteristics of earth formations traversed by a well bore and comprising the steps of: placing fluid-admitting means coupled to a fluid passage with normally-closed valve means arranged therein into sealing engagement with a wall surface of said well bore adjacent to an earth formation believed to contain producible connate fluids for isolating said wall surface from fluids in said well bore and placing one end of said fluid passage into position for subsequently receiving connate fluids from said earth formation; expanding the volume of an enclosed test chamber coupled to said fluid passage downstream of said passage end for reducing the pressure in said fluid passage and said test chamber to about atmospheric pressure; after said test chamber is expanded, opening said valve means at a speed sufficient to quickly induct a sample of producible connate fluids from said earth formation into said expanded test chamber for momentarily reducing the pressure of said connate fluid sample to about atmospheric pressure; and monitoring the pressure in said expanded test chamber for obtaining a series of pressure measurements indicative of the production capabilities of said earth formation.
 10. The method of claim 9 further including the additional step of: recording said pressure measurements for obtaining a record representative of the pressure characteristics of said earth formation as connate fluids are produced therefrom.
 11. The method of claim 9 further including the additional step of: after the pressure-monitoring step, coupling an enclosed sample chamber to said fluid passage for collecting another sample of connate fluids from said earth formation.
 12. The method of claim 11 further including the additional steps of: coupling an additional enclosed sample chamber to said fluid passage for collecting still another sample of connate fluids from said earth formation.
 13. The method of claim 9 further including the additional steps of: after the pressure-monitoring step, reducing the volume of said test chamber for expelling said sample of connate fluids into said well bore; re-closing said valve means; re-expanding the volume of said test chamber for again reducing the pressure in said fluid passage and said test chamber to about atmospheric pressure; after said test chamber is re-expanded, re-opening said valve means at a speed sufficient to quickly induct a second sample of producible connate fluids into said re-expanded test chamber for momentarily reducing the pressure of said second sample to about atmospheric pressure; and re-monitoring the pressure in said re-expanded test chamber for obtaining a second series of pressure measurements indicative of the production capabilities of said earth formation.
 14. The method of claim 13 further including the additional step of: after obtaining said pressure measurements, coupling an enclosed sample chamber to said fluid passage for collecting another sample of connate fluids from said earth formation.
 15. The method of claim 13 further including the additional steps of: after obtaining said pressure measurements, reducing the volume of said test chamber again for expelling said second sample into said well bore; re-closing said valve means; and disengaging said fluid-admitting means from said wall surface.
 16. The method of claim 9 further including the additional steps of: after the pressure-monitoring step, coupling an enclosed sample chamber to said fluid passage for collecting another sample of connate fluids from said earth formation; reducing the volume of said test chamber for expelling said sample of connate fluids into said well bore; re-closing said valve means; re-expanding tHe volume of said test chamber for again reducing the pressure in said fluid passage and said test chamber to about atmospheric pressure; disengaging said fluid-admitting means from said wall surface and placing said fluid-admitting means into sealing engagement with another wall surface of said well bore adjacent to another earth formation believed to contain producible connate fluids for isolating said other wall surface from said well bore fluids; re-opening said valve means at a speed sufficient to quickly induct a second sample of producible connate fluids into said re-expanded test chamber for momentarily reducing the pressure of said second sample to about atmospheric pressure; and re-monitoring the pressure in said re-expanded test chamber for obtaining a second series of pressure measurements indicative of the production capabilities of said other earth formation.
 17. The method of claim 16 further including the additional steps of: after obtaining said second series of pressure measurements, coupling an enclosed sample chamber to said fluid passage for collecting another sample of connate fluids from said other earth formation.
 18. The method of claim 16 further including the additional step of: after obtaining said second series of pressure measurements, reducing the volume of said test chamber again for expelling said second sample into said well bore; re-closing said valve means; and disengaging said fluid-admitting means from said other wall surface.
 19. A method for determining the production characteristics of earth formations traversed by a well bore and comprising the steps of: placing fluid-admitting means including a fluid passage coupled by a filtering medium to an intermediate portion of a fluid-sampling member having a normally-closed forward end and a rearward portion into sealing engagement with a wall surface of said well bore adjacent to an earth formation believed to contain producible connate fluids for isolating said wall surface from fluids in said well bore and placing said closed end of said fluid-sampling member into position for subsequently receiving connate fluids from said earth formation; expanding the volume of an enclosed test chamber coupled to said fluid passage downstream of said filtering medium for reducing the pressure in said fluid passage and said test chamber to about atmospheric pressure; after said test chamber is expanded, opening said closed end of said fluid-sampling member and coupling said test chamber to said fluid passage at a speed sufficient to quickly induct a filtered sample of producible connate fluids from said earth formation into said expanded test chamber for momentarily reducing the pressure of said connate fluid sample to about atmospheric pressure and displacing loose plugging materials from said wall surface into said rearward portion of said fluid-sampling member to the rear of said filtering medium; and monitoring the pressure in said expanded test chamber for obtaining a series of pressure measurements indicative of the production capabilities of said earth formation.
 20. The method of claim 19 further including the additional step of: recording said pressure measurements for obtaining a record representative of the pressure characteristics of said earth formation as connate fluids are produced therefrom.
 21. The method of claim 19 further including the additional step of: after the pressure-monitoring step, coupling an enclosed sample chamber to said fluid passage downstream of said filtering medium for collecting another filtered sample of connate fluids from said earth formation.
 22. The method of claim 21 further including the additional steps of: coupling an additional enclosed sample chamber to said fluid passage downstream of said filtering medium for collecting still another filtered sample of connate fluids from said earth formation.
 23. The method of claim 19 further including the additional stePs of: after the pressure-monitoring step, reducing the volume of said test chamber for expelling said sample of connate fluids into said well bore; uncoupling said test chamber from said fluid passage; re-closing said normally-closed forward end of said fluid-sampling member; re-expanding the volume of said test chamber for again reducing the pressure in said fluid passage and said test chamber to about atmospheric pressure; after said test chamber is re-expanded, re-opening said closed end of said fluid-sampling member and re-coupling said re-expanded test chamber to said fluid passage at a speed sufficient to quickly induct a second filtered sample of producible connate fluids into said re-expanded test chamber for momentarily reducing the pressure of said second sample to about atmospheric pressure and displacing additional loose plugging materials from said wall surface into said rearward portion of said fluid-sampling member to the rear of said filtering medium; and re-monitoring the pressure in said re-expanded test chamber for obtaining a second series of pressure measurements indicative of the production capabilities of said earth formation.
 24. The method of claim 23 further including the additional step of: after obtaining said pressure measurements, coupling an enclosed sample chamber to said fluid passage downstream of said filtering medium for collecting another filtered sample of connate fluids from said earth formation.
 25. The method of claim 23 further including the additional steps of: after obtaining said pressure measurements, reducing the volume of said test chamber again for expelling said second sample into said well bore; re-closing said normally-closed forward end of said fluid-sampling member; and disengaging said fluid-admitting means from said wall surface.
 26. The method of claim 19 further including the additional steps of: after the pressure-monitoring step, coupling an enclosed sample chamber to said fluid passage downstream of said filtering medium for collecting another filtered sample of connate fluids from said earth formation; reducing the volume of said test chamber for expelling said sample of connate fluids into said well bore; uncoupling said test chamber from said fluid passage; re-closing said normally-closed forward end of said fluid-sampling member; re-expanding the volume of said test chamber for again reducing the pressure in said fluid passage and said test chamber to about atmospheric pressure; disengaging said fluid-admitting means from said wall surface and placing said fluid-admitting means into sealing engagement with another wall surface of said well bore adjacent to another earth formation believed to contain producible connate fluids for isolating said other wall surface from said well bore fluids; re-opening said closed end of said fluid-sampling member and re-coupling said re-expanded test chamber to said fluid passage at a speed sufficient to quickly induct a second filtered sample of producible connate fluids into said re-expanded test chamber for momentarily reducing the pressure of said second sample to about atmospheric pressure and displacing loose plugging materials from said other wall surface into said rearward portion of said fluid-sampling member to the rear of said filtering medium; and re-monitoring the pressure in said re-expanded test chamber for obtaining a second series of pressure measurements indicative of the production capabilities of said other earth formation.
 27. The method of claim 26 further including the additional steps of: after obtaining said second series of pressure measurements, coupling an enclosed sample chamber to said fluid passage downstream for collecting another sample of connate fluids from said other earth formation.
 28. The method of claim 26 further including the additional steps of: after obtaining said second series of pressure measurements, reducing the voluMe of said test chamber again for expelling said second sample into said well bore; uncoupling said test chamber from said fluid passage; re-closing said normally-closed end of said fluid-sampling member; and disengaging said fluid-admitting means from said other wall surface.
 29. Formation-testing apparatus adapted for suspension in a well bore traversing earth formations and comprising: a body having a fluid passage adapted to receive connate fluids; fluid-admitting means on said body and adapted to be selectively engaged with a well bore wall for isolating a portion thereof from well bore fluids; means on said body and selectively operable for positioning said fluid-admitting means against a well bore wall to establish communication with earth formations therebeyond; pressure-reducing means on said body and including an enclosed test chamber coupled to said fluid passage and means selectively operable for varying the volume of said test chamber including piston means movable back and forth between a first position reducing the volume of said test chamber and a second position sufficiently expanding the volume of said test chamber to reduce the pressure in said test chamber and said fluid passage to about atmospheric pressure; pressure-measuring means adapted for providing indications representative of the pressure conditions in said test chamber; and control means selectively operable after movement of said piston means to said second position for coupling said fluid-admitting means to said fluid passage at a speed sufficient to induct a sample of producible connate fluids from an earth formation in communication with said fluid-admitting means into said fluid passage and said expanded test chamber for momentarily reducing the pressure of a connate fluid sample to about atmospheric pressure.
 30. The formation-testing apparatus of claim 29 further including: sample-collecting means on said body including a sample chamber, and means selectively operable for coupling said sample chamber to said fluid passage to receive connate fluids entering said fluid-admitting means.
 31. The formation-testing apparatus of claim 29 wherein said control means include: valve means cooperatively arranged between said fluid-admitting means and said fluid passage and normally closing one end of said fluid passage.
 32. The formation-testing apparatus of claim 31 further including: sample-collecting means on said body including a sample chamber, and means selectively operable for coupling said sample chamber to said fluid passage to receive connate fluids entering said fluid-admitting means.
 33. Formation-testing apparatus adapted for suspension in a well bore traversing earth formations and comprising: a body having a fluid passage adapted to receive connate fluids; fluid-admitting means on said body and including a fluid-sampling member adapted to be selectively engaged with a well bore wall for isolating a portion thereof from well bore fluids; means on said body and selectively operable for positioning said fluid-admitting means against a well bore wall to place said fluid-sampling member in communication with earth formations beyond said well bore wall; pressure-reducing means on said body and including an enclosed test chamber coupled to said fluid passage and means selectively operable for varying the volume of said test chamber including piston means movable back and forth between a first position reducing the volume of said test chamber and a second position sufficiently expanding the volume of said test chamber to reduce the pressure in said test chamber and said fluid passage to about atmospheric pressure; pressure-measuring means adapted for providing indications representative of the pressure conditions in said test chamber; and control means selectively operable after movement of said piston means to said second position including normally-closed valve means cooperatively arrangeD for coupling said fluid passage to said fluid-sampling member at a speed sufficient to induct a sample of producible connate fluids from an earth formation in communication with said fluid-sampling member into said fluid passage and said expanded test chamber for momentarily reducing the pressure of a connate fluid sample to about atmospheric pressure.
 34. The formation-testing apparatus of claim 33 further including: a sample chamber on said body, and second normally-closed valve means selectively operable for coupling said sample chamber to said fluid passage to receive connate fluids entering said fluid-sampling member.
 35. The formation-testing apparatus of claim 33 further including: filtering means on said fluid-sampling member adapted for straining connate fluids entering said fluid passage upon opening of said valve means.
 36. The formation-testing apparatus of claim 35 further including: a sample chamber on said body, and second normally-closed valve means selectively operable for coupling said sample chamber to said fluid passage to receive connate fluids entering said fluid-sampling member. 